1. Field of the Invention
The present invention is directed to the sampling of ambient air and separation and collection of particulate matter fractions (PM) from the sample.
2. The Related Art
Airborne particulate matter, known as PM, is one of the major components of smog. PM includes microscopic particles in the air that are divided into two size ranges: PM2.5 and PM 10. PM2.5 refers to “fine” particles less than 2.5 micrometers (microns) in size about 1/20th the width of a human hair. Likewise, PM10 refers to particles less than 10 microns in size. As used herein, “coarse” has reference to a PM fraction 2.5-10 microns in size.
PM can be released directly to the atmosphere from such sources as industrial smokestacks, automobile tailpipes, wood burning and road dust, to mention a few. PM can also form in the atmosphere from chemical reactions involving other pollutants such as sulphur dioxide (SO2), nitrogen oxides (NOX), ammonia (NH3), and volatile organic compounds (VOC).
According to a New Scientist article (Inside Science, No. 84, 1995) large particles are filtered out by the nose. Middle size particles deposited in the airways are trapped on a layer of mucus which sweeps them to the throat, where they are coughed up or swallowed. Only particles less than 2 microns reach the alveoli, where they must be dealt with by macrophages from the immune system. Particles less than 2 microns in size can be inhaled deep into the lungs and reach the critical areas where the cells replenish the blood with oxygen. They can cause breathing and respiratory symptoms, irritation, inflammation and damage to the lungs. Health studies have shown significant associations between exposure to PM2.5 and premature death from heart or lung disease. Fine particles (PM2.5) also aggravate heart and lung diseases and have been linked to effects such as cardiovascular symptoms, cardiac arrhythmias, congestive heart failure, heart attacks, respiratory symptoms, asthma attacks, and bronchitis. These effects can result in increased hospital admissions, emergency room visits, absences from school or work, and restricted activity days. Individuals that may be particularly sensitive to PM2.5 exposure include people with heart or lung disease, older adults and children.
Accordingly, the U.S.E.P.A. has published rules setting forth air quality designations and classifications for fine particulates (PM2.5) pursuant to the National Ambient Air Quality Standards (NAAQS).
Despite the growing evidence of particulate-related health effects, the paucity of information about specific biological mechanisms remains a critical missing link.
In addition to PM2.5, coarse PM (2.5-10 μm in aerodynamic diameter) may also consist of several potentially toxic components, such as resuspended particulate matter from paved and unpaved roads, industrial materials, brake linings, tire residues, trace metals, and bioaerosols. A considerable fraction of these particles may deposit in the upper airways and to a lesser extent into the lower airways, and may be responsible for the exacerbation of asthma. Recent data from a small number of epidemiological studies indicate that, apart from—or in addition to—the fine PM fraction, health effects may also be closely associated with the coarse PM fraction and sometimes even to a larger extent (Ostro et al., 1999, Kleinman et al., 2000) than PM2.5. In vitro studies with human monocytes (Monn and Becker, 1998; Becker et al., 1996) show that cellular toxicity and inflammation may also be associated with the coarse fraction (2.5-10 μm) and its biological components. Also, in vitro data from Romberg et at. (1998a,b) on genotoxicity of ambient fine and coarse mode PM collected from an urban area characterized by a high traffic density suggests that coarse mode PM may have comparable or even higher activity. Collectively, these studies indicated that the coarse mode PM might still contribute to a certain extent to observed health effects, especially those occurring in the higher airways like asthma.
Accordingly, a need exists for sampling ambient air, and separating particulates therefrom as coarse and fine fractions separated by a sharp cut point at 2.5 microns.